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Results for “ADAPTATION, PHYSIOLOGICAL”

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PubMed2002

Over-representation of repeats in stress response genes: a strategy to increase versatility under stressful conditions?

The survival of individual organisms facing stress is enhanced by the induction of a set of changes. As the intensity, duration and nature of stress is highly variable, the optimal response to stress may be unpredictable. To face such an uncertain future, it may be advantageous for a clonal population to increase its phenotypic heterogeneity (bet-hedging), ensuring that at least a subset of cells would survive the current stress. With current techniques, assessing the extent of this variability experimentally remains a challenge. Here, we use a bioinformatic approach to compare stress response genes with the rest of the genome for the presence of various kinds of repeated sequences, elements known to increase variability during the transfer of genetic information (i.e. during replication, but also during gene expression). We investigated the potential for illegitimate and homologous recombination of 296 Escherichia coli genes related to repair, recombination and physiological adaptations to different stresses. Although long repeats capable of engaging in homologous recombination are almost absent in stress response genes, we observed a significant high number of short close repeats capable of inducing phenotypic variability by slipped-mispair during DNA, RNA or protein synthesis.

Adaptation, Physiological↗

PubMed2002

Biochemical responses to iron deficiency in kiwifruit (Actinidia deliciosa).

A comparative study of two kiwifruit genotypes (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson var. deliciosa) with different tolerance to iron (Fe) deficiency was conducted to identify biochemical features associated with tolerance to Fe deficiency. After 14 days of growth in hydroponic culture under Fe-deficient and Fe-sufficient conditions, leaf chlorophyll concentration, activities of ferric chelate reductase (FCR), phosphoenolpyruvate carboxylase (PEPC) and citrate synthase in root extracts, concentrations of organic acids in roots, leaves and xylem sap, and xylem sap pH were measured. In response to Fe deficiency, the tolerant genotype D1 showed: (i) higher FCR activity associated with a longer lasting induction of FCR; (ii) higher PEPC activity; (iii) higher concentrations of citric acid in roots; and (iv) lower xylem sap pH compared with the susceptible genotype Hayward. These findings imply that induction of FCR and PEPC activities in roots in response to Fe deficiency are important physiological adaptations enabling Fe-efficient kiwifruit plants to tolerate Fe deficiency.

Actinidia↗

PubMed1997

Electromyographic analysis of muscle fatigue in anterior cruciate ligament deficient knees.

The aim of this study was to detect possible differences in muscle fatigue and recovery of knee flexor and extensor muscles in patients with a deficient anterior cruciate ligament compared with patients with a normal anterior cruciate ligament. Surface electromyography of 15 patients with anterior cruciate ligament deficiency was performed while the muscles were under 80% of maximum isometric contraction, and after 1, 2, 3, and 5 minutes of rest. During the first 60 seconds of contraction, all muscles recorded significantly decreased mean power frequency and increased amplitude. The rate of decrease of mean power frequency was significantly greater in the injured quadriceps and normal hamstrings. All muscles except two recovered to the initial mean power frequency level after 1 minute of rest. All but two muscles in the injured and normal limb recorded an overshoot of mean power frequency during the recovery phase. This overshoot phenomenon also was seen for some muscles in the amplitude analysis. The findings confirm the fatigue state in all the muscles, suggest recruitment of more Type II fibers as the muscle fatigues, and show the physiologic adaptation of the quadriceps and hamstrings to anterior cruciate ligament insufficiency. The current study indirectly shows a dissociation between low intramuscular pH and mean power frequency during the recovery phase. It also indirectly suggests that the atrophied thigh muscles have fiber type composition similar to that of the normal side.

Adaptation, Physiological↗

PubMed2001

Resistance training enhances the stability of sensorimotor coordination.

Strategies for the control of human movement are constrained by the neuroanatomical characteristics of the motor system. In particular, there is evidence that the capacity of muscles for producing force has a strong influence on the stability of coordination in certain movement tasks. In the present experiment, our aim was to determine whether physiological adaptations that cause relatively long-lasting changes in the ability of muscles to produce force can influence the stability of coordination in a systematic manner. We assessed the effects of resistance training on the performance of a difficult coordination task that required participants to synchronize or syncopate movements of their index finger with an auditory metronome. Our results revealed that training that increased isometric finger strength also enhanced the stability of movement coordination. These changes were accompanied by alterations in muscle recruitment patterns. In particular, the trained muscles were recruited in a more consistent fashion following the programme of resistance training. These results indicate that resistance training produces functional adaptations of the neuroanatomical constraints that underlie the control of voluntary movement.

Acoustic Stimulation↗

PubMed1994

Physical health status in young subjects after colectomy: an application of the Roy model.

The aim of this study was to describe the long-term physical health status after colectomy in 30 young subjects with ulcerative colitis, 11 of whom had ileostomies. The subjects, aged between 14 and 31 years of age, were assessed post-operatively for their physical health status. In assessing physiological adaptation in these subjects four basic needs were the foci: nutrition, elimination, activity and rest, and protection. Adaptation problems related to nutrition, elimination, activity/rest and protection were found in four, 17, 17 and three subjects respectively. Nine out of 30 had pain that influenced their daily life. Six out of 30 subjects had no adaptation problems at all. Nineteen subjects found their health to be 'excellent' or 'good' despite the adaptation problems reported.

Adaptation, Physiological↗

PubMed2001

Early life influences on later health: the role of nutrition.

Individuals who were small at birth have an increased risk of cardiovascular disease in later life. Barker has put forward a hypothesis to explain this and other associations, known as the 'fetal origins theory of adult disease'. It is proposed that chronic disease is the long-term outcome of physiological adaptations the unborn baby makes when it is undernourished, a process referred to as 'programming'. Maternal nutrition is thought to be a major influence on programming, and growth in childhood as well as obesity in later life may modulate the propensity for disease acquired in the womb. While robust evidence to support specific nutritional interventions during pregnancy is currently lacking, the theory in general affirms broader public health nutritional strategies and policies to improve the social and economic status of women.

Adaptation, Physiological↗

PubMedDate not supplied

Childbearing in space. A theoretical perspective.

Nursing care for the childbearing woman in microgravity will be the challenge of the future. The purpose of this theoretical article is to stimulate creative thought. Information garnered through years of research in obstetrics and, more recently, in space medicine is reviewed. Physiologic adaptations occur as a result of both pregnancy and space flight. The potential interplay of these changes is discussed, and questions are raised for further consideration.

Adaptation, Physiological↗

PubMed2005

Hindlimb unweighting for 2 weeks alters physiological properties of rat hindlimb motoneurones.

We sought to determine whether decreased neuromuscular use in the form of hindlimb unweighting (HU) would affect the properties of innervating motoneurones. Hindlimb weight-bearing was removed in rats for a period of 2 weeks via hindlimb suspension by the tail. Following this the electrophysiological properties of tibial motoneurones were recorded under anaesthesia in situ. After HU, motoneurones had significantly (P < 0.05) elevated rheobase currents, lower antidromic spike amplitudes, lower afterhyperpolarization (AHP) amplitudes, faster membrane time constants, lower cell capacitances, and depolarized spike thresholds. Frequency-current (f-I) relationships were shifted significantly to the right (i.e. more current required to obtain a given firing frequency), although there was no change in f-I slopes. 'Slow' motoneurones (AHP half-decay times, > 20 ms) were unchanged in proportions in HU compared to weight-bearing rats. Slow motoneurones had significantly lower minimum firing frequencies and minimum currents necessary for rhythmic firing than 'fast' motoneurones in weight-bearing rats; these differences were lost in HU rats, where slow motoneurones resembled fast motoneurones in these properties. In a five-compartment motoneurone model with ion conductances incorporated to resemble firing behaviour in vivo, most of the changes in passive and rhythmic firing properties could be reproduced by reducing sodium conductance by 25% and 15% in the initial segment and soma, respectively, or by increasing potassium conductance by 55% and 42%, respectively. This supports previous conclusions that changes in chronic neuromuscular activity, either an increase or decrease, may result in physiological adaptations in motoneurones due to chronic changes in ion conductances.

Action Potentials↗

PubMed2006

Differential regulation of metabolic genes in skeletal muscle during starvation and refeeding in humans.

This study investigated the molecular alterations underlying the physiological adaptations to starvation and refeeding in human skeletal muscle. Forty-eight hours' starvation reduced whole-body insulin sensitivity by 42% and produced marked changes in expression of key carbohydrate (CHO) regulatory genes and proteins: SREBP1c and hexokinase II (HKII) were downregulated 2.5- and 5-fold, respectively, whereas the pyruvate dehydrogenase kinase 4 (PDK4) was upregulated 4-fold. These responses were not dependent on the phosphorylation status of Akt and FOXO1. On the other hand, starvation and the concomitant increase in circulating free fatty acids did not upregulate the expression of transcription factors and genes involved in fat metabolism. Twenty-four hours' refeeding with a CHO-rich diet completely reversed the changes in PDK4, HKII and SREBP1c expression in human skeletal muscle but failed to fully restore whole-body insulin sensitivity. Thus, during starvation in healthy humans, unlike rodents, regulation of fat metabolism does not require an adaptive response at transcriptional level, but adaptive changes in gene expression are required to switch off oxidative glucose disposal. Lack of effect on key proteins in the insulin-signalling pathway may indicate that changes in intracellular substrate availability/flux may be responsible for these adaptive changes in glucose metabolism. This may represent an important aspect of the molecular basis of the development of insulin resistance in metabolic conditions characterized by energy restriction.

Adaptation, Physiological↗

PubMed2002

Nutritional intake of French soccer players at the clairefontaine training center.

Young, French male athletes undergoing intensive elite sports training at the National Training Centre in Clairefontaine served as the subjects (N = 180; age range: 13 to 16 years) in a 3-year dietary survey aimed at characterizing their nutritional intake in terms of energy, macronutrients, calcium, and iron. Each year, the subjects were grouped by level into 3 promotions so that 9 groups could be studied. Dietary intake data were collected each year for each subject in the 9 groups, using a 5-day food record. The results showed that their total energy intake (TEI) was insufficient for athletes (ranging from 2352 454 to 3395 396 kcal/d as opposed to the recommended range of between 3819 and 5185 kcal/d). Furthermore, their diet was unbalanced, with too great an emphasis upon fatty foods (29.1 2.8 to 34.1 3.1% TEI vs. the 20% recommended), to the detriment of carbohydrates (48.5 4.3 to 56.6 3.1% TEI vs. the 55 to 60% recommended). The calcium intake was too low in 5 of the 9 groups while, in contrast, the iron intake was satisfactory in all groups. Furthermore, during this 3-year period at the Clairefontaine Centre, the subjects significantly (p <.05) improved their calcium and iron intakes (1021 197 and 12 2 mg/d in 1996, 1299 155 and 16 2 mg/d in 1997, and 1252 184 and 17 2 mg/d in 1998). This rise in micronutrient intakes may have been due to a physiological adaptation to growth or to the positive effects of courses on nutrition given during their stay at the Centre.

Adaptation, Physiological↗

PubMed1997

A novel RNA species from the turtle mitochondrial genome: induction and regulation of transcription and processing under anoxic and freezing stresses.

The present study identifies a previously cloned cDNA, pBTaR914, as homologous to the mitochondrial WANCY (tryptophan, alanine, asparagine, cysteine, and tyrosine) tRNA gene cluster. This cDNA clone has a 304-bp sequence and its homologue, pBTaR09, has a 158-bp sequence with a long poly(A)+ tail (more than 60 adenosines). RNA blotting analysis using pBTaR914 probe against the total RNA from the tissues of adult and hatchling turtles revealed five bands: 540, 1800, 2200, 3200, and 3900 nucleotides (nt). The 540-nt transcript is considered to be an intact mtRNA unit from a novel mtDNA gene designated WANCYHP that overlaps the WANCY tRNA gene cluster region. This transcript was highly induced by both anoxic and freezing stresses in turtle heart. The other transcripts are considered to be the processed intermediates of mtRNA transcripts with WANCYHP sequence. All these transcripts were differentially regulated by anoxia and freezing in different organs. The data suggest that mtRNA processing is sensitive to regulation by external stresses, oxygen deprivation, and freezing. Furthermore, the fact that the WANCYHP transcript is highly induced during anoxic exposure suggests that it may play an important role in the regulation of mitochondrial activities to coordinate the physiological adaptation to anoxia.

Adaptation, Physiological↗

PubMed2004

Physiological hypertrophy of the FHL muscle following 8 weeks of progressive resistance exercise in the rat.

In humans, progressive resistance exercise is recognized for its ability to induce skeletal muscle hypertrophy. In an attempt to develop an animal model which mimics human progressive resistance exercise, Sprague-Dawley rats were trained to climb a 1.1-m vertical (80 degree incline) ladder with weights secured to their tail. The rats were trained once every 3 days for 8 weeks. Each training session consisted of 4-9 (6.02 +/- 0.23) climbs requiring 8-12 dynamic movements per climb. Based on performance, the weight carried during each session was progressively increased. Over the course of 8 weeks, the maximal amount of weight the rats could carry increased 287%, p </= 0.001. The improved training performance was associated with a 23% absolute increase in the weight of the flexor hallucis longus (FHL), with a concomitant 24% increase in both total and myofibrillar protein, p</= 0.001. Peak tetanic tension (Po) of the FHL increased 20%, p </= 0.001, while specific tetanic tension (SPo) was not altered. No change in twitch tension (Pt) was observed, which resulted in a 22% decrease in specific twitch tension (SPt) p </= 0.01. Despite a decrease in resistance to fatigue, p </= 0.05, myosin heavy chain composition, ATP, ADP, creatine, and creatine phosphate concentrations of the FHL were not altered. The results of this study describe an animal model that mimics many of the training parameters and physiological adaptations observed with human progressive resistance exercise.

Adaptation, Physiological↗

PubMed2005

VO2 responses to intermittent swimming sets at velocity associated with VO2max.

While the physiological adaptations following endurance training are relatively well understood, in swimming there is a dearth of knowledge regarding the metabolic responses to interval training (IT). The hypothesis tested predicted that two different endurance swimming IT sets would induce differences in the total time the subjects swam at a high percentage of maximal oxygen consumption (VO(2)max). Ten trained triathletes underwent an incremental test to exhaustion in swimming so that the swimming velocity associated with VO(2)max (vVO(2)max) could be determined. This was followed by a maximal 400-m test and two intermittent sets at vVO(2)max: (a) 16 x 50 m with 15-s rest (IT(50)); (b) 8 x 100 m with 30-s rest (IT(100)). The times sustained above 95% VO(2)max (68.50 +/- 62.69 vs. 145.01 +/- 165.91 sec) and 95% HRmax (146.67 +/- 131.99 vs. 169.78 +/- 203.45 sec, p = 0.54) did not differ between IT(50) and IT(100)(values are mean +/- SD). In conclusion, swimming IT sets of equal time duration at vVO(2)max but of differing work-interval durations led to slightly different VO(2)and HR responses. The time spent above 95% of VO(2)max was twice as long in IT(100) as in IT (50), and a large variability between mean VO(2)and HR values was also observed.

Adaptation, Physiological↗

PubMed2005

Application of animal models: chronic electrical stimulation-induced contractile activity.

Unilateral, chronic low-frequency electrical stimulation (CLFS) is an experimental model that evokes numerous biochemical and physiological adaptations in skeletal muscle. These occur within a short time frame and are restricted to the stimulated muscle. The humoral effects of whole body exercise are eliminated and the nonstimulated contralateral limb can often be used as a control muscle, if possible effects on the contralateral side are considered. CLFS induces a fast-to-slow transformation of muscle because of alterations in calcium dynamics and myofibrillar proteins, and a white-to-red transformation because of changes in mitochondrial enzymes, myoglobin, and the induction of angiogenesis. These adaptations occur in a coordinated time-dependent manner and result from altered gene expression, including transcriptional and posttranscriptional processes. CLFS techniques have also been applied to myocytes in cell culture, which provide a greater opportunity for the delivery of pharmacological agents or for the application of gene transfer methodologies. Clinical applications of the CLFS technique have been limited, but they have shown potential therapeutic value in patients in whom voluntary muscle contraction is not possible due to debilitating disease and/or injury. Thus the CLFS technique has great value for studying various aspects of muscle adaptation, and its wider scientific application to a variety of neuromuscular-based disorders in humans appears to be warranted.

Adaptation, Physiological↗

PubMed2004

Regulation of dihydropyridine receptor gene expression in mouse skeletal muscles by stretch and disuse.

This study examined dihydropyridine receptor (DHPR) gene expression in mouse skeletal muscles during physiological adaptations to disuse. Disuse was produced by three in vivo models-denervation, tenotomy, and immobilization-and DHPR alpha1s mRNA was measured by quantitative Northern blot. After 14-day simultaneous denervation of the soleus (Sol), tibialis anterior (TA), extensor digitorum longus (EDL), and gastrocnemius (Gastr) muscles by sciatic nerve section, DHPR mRNA increased preferentially in the Sol and TA (+1.6-fold), whereas it increased in the EDL (+1.6-fold) and TA (+1.8-fold) after selective denervation of these muscles by peroneal nerve section. It declined in all muscles (-1.3- to -2.6-fold) after 14-day tenotomy, which preserves nerve input but removes mechanical tension. Atrophy was comparable in denervated and tenotomized muscles. These results suggest that factor(s) in addition to inactivity per se, muscle phenotype, or associated atrophy can regulate DHPR gene expression. To test the contribution of passive tension to this regulation, we subjected the same muscles to disuse by limb immobilization in a maximally dorsiflexed position. DHPR alpha1s mRNA increased in the stretched muscles (Sol, +2.3-fold; Gastr, +1.5-fold) and decreased in the shortened muscles (TA, -1.4-fold; EDL, -1.3-fold). The effect of stretch was confirmed in vitro. DHPR protein did not change significantly after 4-day immobilization, suggesting that additional levels of regulation may exist. These results demonstrate that DHPR alpha1s gene expression is regulated as an integral part of the adaptive response of skeletal muscles to disuse in both slow- and fast-twitch muscles and identify passive tension as an important signal for its regulation in vivo.

Adaptation, Physiological↗

PubMed1989

Effect of long-term tilt on mechanical and electrical properties of rat saphenous vein.

Femoral vein pressure in adult male Sprague-Dawley rats kept in specially designed tubelike cages rose immediately from a control value of 2.9 +/- 0.2 (SE) mmHg to a gravity-induced sustained value of 5.9 +/- 0.2 mmHg on initiation of a 2-wk 45 degrees head-up tilt period. Femoral arterial pressure was not altered by tilting. In 2 wk mean external diameter, but not total wall thickness, of in vitro distal saphenous vein segments from tilted rats was increased approximately 30% above that of segments from nontilted controls at each of four successive 5-mmHg intralumenal pressure (IP) increments applied between 0 and 20 mmHg. Consequently, in tilted rats isobaric stress was increased 38% at low and 24% at high IP, whereas incremental distensibility was decreased at mid IP. Vascular smooth muscle (VSM) in tilted rat vein, but not artery, was hyperpolarized relative to controls both in vitro at normal physiological pressures [membrane potential (Em) = -58.2 +/- 0.8 vs. -52.4 +/- 0.8 mV, respectively] and in situ during local neural blockade (Em = -61.3 +/- 2.3 vs. -53.5 +/- 0.5 mV, respectively). The conclusion is that a moderate chronic elevation of IP in a vein results in hyperpolarization of its VSM and an elevation of its total capacity due to an as yet unexplained mechanism of physiological adaptation.

Adaptation, Physiological↗

PubMed1982

Effect of chronic altitude hypoxia on hematologic and glycolytic parameters.

The physiological effect of chronic exposure to altitude hypoxia on the glycolytic intermediates, adenosine triphosphate and 2,3-diphosphoglyceric acid, and the hematologic parameters, hemoglobin, hematocrit, and mean cell hemoglobin concentration, has been examined in an indigenous population, the Aymara, of the Departamento de Arica, Chile. This population normally resides at three altitudes: the coast (0-500 m), the sierra (2,500-3,500 m), and the altiplano (above 4,200 m). After isolation of altitude from other environmental factors (age, sex, body build, ethnicity, smoking, and residential permanence), an increase in 2,3-diphosphoglycerate and a decrease in adenosine triphosphate was observed. Both hemoglobin and hematocrit increased as expected, but mean cell hemoglobin concentration declined. It is proposed that a decline in the activity of a single enzyme, pyruvate kinase, can account for these observed changes and suggests a pivotal role for pyruvate kinase in the physiological adaptation to altitude hypoxia.

2,3-Diphosphoglycerate↗

PubMed1984

Regulation of metabolic rate in Svalbard and Norwegian reindeer.

Food intake, body weight, serum levels of triiodothyronine (T3) and free thyroxine (FT4), and metabolic rate were measured at intervals in Svalbard (SR) and Norwegian (NR) reindeer. From summer to winter food intake decreased 57 (SR) and 55% (NR), while body weight decreased 8.6 (SR) and 3.8% (NR). In SR T3 and FT4 changed seasonally, whereas this was only evident for T3 in NR. Resting (standing) metabolic rate (RMR) in winter was 1.55 (SR) and 2.05 W X kg-1 (NR), lower critical temperature (TLC) being -50 (SR) and -30 degrees C (NR). RMR in summer was 2.15 (SR) and 2.95 W X kg-1 (NR), TLC being -15 (SR) and 0 degrees C (NR). Seasonal changes in T3 and FT4 did not coincide with changes in food intake or RMR in either SR or NR. RMR did, however, correlate with food intake. This indicates that seasonal changes in RMR are due to the thermic effects of feeding and represent no physiological adaptation aimed at conservation of energy during winter.

Adaptation, Physiological↗